Effects of contrast polarity in paracontrast masking

The visibility of a target stimulus can be suppressed (inhibition) or increased (facilitation) during paracontrast masking. Three processes have been proposed to be involved in paracontrast masking: brief inhibition, facilitation, and prolonged inhibition (Breitmeyer et al., 2006). Brief inhibition is observed when the mask precedes the target at short stimulus onset asynchronies (SOAs) ranging from -10 to -30 msec, whereas prolonged inhibition is effective up to very large SOAs of -450 msec. Facilitation, enhancement in target visibility, can be observed at SOA values between -20 and -110 msec. We further investigated these processes by changing target-mask spatial separation and the contrast polarity of the mask. Our results show that (1) facilitation weakens when spatial separation between the target and mask is increased or when they have opposite contrast polarity, and (2) brief inhibition turns into facilitation for the opposite-polarity mask, whereas prolonged inhibition does not change significantly. These results suggest a fast inhibition mechanism realized in the contrast-specific center-surround antagonism of classical receptive fields for brief inhibition and a slower, higher level cortical processing that is indifferent to contrast polarity for prolonged inhibition.     

Mapping across Domains Without Feedback: A Neural Network Model of Transfer of Implicit Knowledge

This paper shows how a neural network can model the way people who have acquired knowledge of an artificial grammar in one perceptual domain (e.g., sequences of tones differing in pitch) can apply the knowledge to a quite different perceptual domain (e.g., sequences of letters). It is shown that a version of the Simple Recurrent Network (SRN) can transfer its knowledge of artificial grammars across domains without feedback. The performance of the model is sensitive to at least some of the same variables that affect subjects' performance—for example, the model is responsive to both the grammaticality of test sequences and their similarity to training sequences, to the cover task used during training, and to whether training is on bigrams or larger sequences.     

Impact of artificial fissioning and social networks on levels of aggression and affiliation in primates

Levels of aggression may be affected by stability of social relationships or by population density. A number of studies of nonhuman primates have indicated that spatial density influences agonistic activity levels less than does social density. Artificial fissioning of a captive troop of rhesus macaques was undertaken and the resultant differences in patterns of aggression and affiliation were examined. If population density has a major effect on levels of aggression, then fissioning will result in a decrease in aggression; if social stability has a major effect on levels of aggression, then fissioning is likely to be accompanied by an increase in aggression. An increase in rates of both aggressive and affiliative behavior resulted from artificial troop fissioning. These findings concur with other studies that have concluded that social stability is a more important determinant of primate aggression than is population density. Nonhuman primates use affiliative mechanisms to adjust their behavior when population density increases such that potentially adverse consequences of crowding are avoided.     

Does IOR occur in discrimination tasks? Yes, it does, but later

When a stimulus appears in a previously cued location several hundred milliseconds after the cue, the time required to detect that stimulus is greater than when it appears in an uncued location. This increase in detection time is known as inhibition of return (IOR). It has been suggested that IOR reflects the action of a general attentional mechanism that prevents attention from returning to previously explored loci. At the same time, the robustness of IOR has been recently disputed, given several failures to obtain the effect in tasks requiring discrimination rather than detection. In a series of eight experiments, we evaluated the differences between detection and discrimination tasks with regard to IOR. We found that IOR was consistently obtained with both tasks, although the temporal parameters required to observe IOR were different in detection and discrimination tasks. In our detection task, the effect appeared after a 400-msec delay between cue and target, and was still present after 1,300 msec. In our discrimination task, the effect appeared later and disappeared sooner. The implications of these data for theoretical accounts of IOR are discussed.     

Implicit synthesis

In this reply to Neal and Hesketh and to the commentators, we argue that implicit knowledge is partly abstract and can be usefully defined by the criteria of both metaknowledge and intentional control. We suggest that the pattern of dissociations supports a claim of separate implicit and explicit learning modes. According to our characterization, implicit learning leads to knowledge that is not automatically represented as knowledge by the learning process; instead, the presence of knowledge has to be inferred by the subject (partial explicitation) if metaknowledge is gained at all. During explicit learning, knowledge is automatically labeled as knowledge by the learning process, so that metaknowledge comes immediately and to the fullest extent. Finally, we suggest that implicit knowledge may to some degree apply regardless of intention.     

The importance of prudent negative consequences for maintaining the appropriate behavior of hyperactive students

Teachers use both positive and negative consequences to influence classroom behaviors. Four experiments were conducted to examine the differential affects of these two types of consequences on the maintenance of appropriate behaviors of hyperactive children. Results of Experiment 1 showed that the use of both positive and negative consequences (combined) was associated with high levels of on-task behaviors. Withdrawal of negative consequences caused a significant and dramatic decrease in on-task performance. The withdrawal of positive consequences produced no change in the rate of on-task behaviors. In Experiments 2, 3, and 4, the on-task results of Experiment 1 were replicated using a different teacher, different children, a counterbalanced design, longer phases, and different types of negative consequences. The withdrawal of negative consequences led to decreases in productivity in Experiment 2. The results of Experiment 3 also suggested that a prudent (e.g., calm, concrete, and consistent) approach to discipline was more effective than an imprudent (e.g., loud, emotional, and inconsistent) approach. Some level of mild negative consequences for inappropriate behavior is an important ingredient in effective classroom management, and qualitatively different negative consequences may have drastically different effects on the behavior of hyperactive students.This research was supported in part by a grant from the Middle Country Central School District No. 11, Centereach, New York, to the second author. We are grateful for the district's continued support. In addition, the authors wish to thank K. Daniel O' Leary for his helpful editorial comments.     

Beliefs, attitudes, and intention in the context of abortion

Women's beliefs, attitudes, and intention, defined according to Fishbein and Ajzen (1975), were studied in relation to procedures for abortion: a commonly used surgical method, vacuum aspiration, and a recent medical alternative. Subjects were 53 women requesting an abortion and 53 nonpregnant women. Effects of having had an abortion prior to the study and of situation were obtained as expected in belief ratings and attitude measures. Choice of the medical alternative was related to having distinctly opposite attitudes to methods. Choice of the surgical treatment related to having slightly negative attitudes to both methods. In the actual situation more positive attitudes had been expected and were obtained. Previous experience of abortion and situation were assumed to be external factors with effects on intention if mediated by the attitudes. A logistic regression model showed a good fit and predicted the intentional choice of treatment from attitude scores.     

An empirical test of two opposing theoretical models of prefrontal function.

The purpose of this study was to compare the validity of two models which contrast with each other in the manner in which they integrate neuropsychological tests into distinct prefrontal constructs. The first prefrontal model consists of five distinct functional constructs drawn from human clinical neuropsychology. The second model, elaborated by Goldman-Rakic, is based primarily on monkey research and postulates a basic prefrontal function, "on-line representational memory," which guides behavior in the absence of, or despite discriminative environmental stimuli. In the latter model, distinct prefrontal functional constructs are primarily defined in terms of various types of representational memory involved in specific tasks. Eleven "prefrontal" measures were obtained from 259 normal adults, stratified for age, education, and sex. Confirmatory factor analyses revealed that the Goldman-Rakic model "fit" the data better than the model derived from human clinical neuropsychology, while several constructs commonly used in human neuropsychology were refuted. It was concluded that new research on brain-damaged humans with a view to understanding prefrontal function might benefit from using the Goldman-Rakic model as a starting point.     

Continuous self-recording of epigastric pain with two rating scales: Compliance,authenticity, reliability,and sensitivity

The present study compared two self-recording scales: VAS (Visual Analogue Scale) and DIBS (Duration, Intensity, Behavior Scale) with respect to compliance, authenticity, sensitivity, and reliability using a population of 32 patients with chronic epigastric pain. Compliance, authenticity, and sensitivity data revealed no significant differences between the two scales. With respect to reliability, high temporal stability coefficients were found for pain intensity over a 2-day period, for pain duration, and for a pain index calculated from DIBS. DIBS pain intensity data showed a greater temporal stability than VAS. Since DIBS yields more clinically useful information without suffering deficits in compliance, authenticity, or reliability, it appears to be a preferable instrument for monitoring chronic pain.